In operation of pipeline connected equipment, including pipelines which stretch across the open country and also including facilities where the pipeline may only be a few hundred feet in length, it is necessary to periodically conduct pigging operations. A pipeline pig is a cleaning device which is placed in the pipeline and transmitted along the pipeline with the fluid flow for cleaning. Sometimes it is used for batch separation. Pipeline pigs are also used in food manufacturing plants to periodically clean the lines to prevent the accumulation of deposits and the like which result from sedimentation or perhaps drying of particles. For instance, in plants which make liquid products such as catsup and the like, it is necessary for the sake of cleanliness to periodically pump a pig through the pipelines in the plant.
These pigs are normally sized to match the size of the pipeline. As a generalization, it is necessary to clean such pipelines often, but the frequency is in part dependent on the nature of the product flowing through the pipeline. In the handling of food products, it may be necessary to often pig the line, for instance once per day when the equipment is shut down and wash water is pumped through the lines to clear the lines. In that instance, it might be necessary to pump water through the line, then pig the line and thereafter pump more water through the line to remove deposits and accumulations within the pipeline. In a large food processing plant, there might be many points of entry for pigs at various locations because the plant can have numerous pipelines and it is therefore necessary to know the precise whereabouts of all pigs that are placed in the piping system. Ordinarily, the pipes are made of metal and they are not transparent. Occasionally, translucent or clear line material will be used, but it generally will not stand up, and it also provides a different kind of surface which may attract and hold an excessive amount of debris, deposits and the like, thereby increasing the risk of spoilage of the product.
In a milk processing plant it is desirable that certain types of stainless steel be used. In other food processing plants it is again typically required that the pipes and connective lines be formed of stainless steel, and in that setting, it is very difficult to locate the pipeline pigs. It is highly undesirable that a pig be left in the line after food processing begins in the next work shift.
The present apparatus is a pipeline pig passage indicator which provides a signal. This signal is formed after the pig has traversed the pipeline. In a large food processing plant, it might be necessary to install as many as 400 to 500 units of the pigs passage indicators so that pig whereabouts can be determined in view of the fact that the lines are circuitous, and may connect with numerous valves so that the pigs are intended to travel in a particular direction are not permitted to be diverted and found elsewhere at the plant. Accordingly, a pig passage indicator is an extremely important device to know with certainty the location or whereabouts of a pig in the plant. The present apparatus sets forth such a device and equipment.
Pig passage indicators are believed to be old. Many have been developed for transcontinental pipelines where the pig is a very large object. To avoid intrusion in the pipeline, magnetic pig detectors can be used especially where the pig is formed with metal. A common type of pig includes a metal core or spine which extends the length of the pig and which supports resilient cups, wipers or the like deployed around the central metal member. That can be easily picked up by a magnetic detector which observes a change in flux with the passage of the ferrous materials making up the pig body. The present apparatus is a pig passage indicator which responds to the passage of a pig which is substantially full gauge in the pipeline. By that, reference is made to the fact that it responds to a pig which fills the pipeline because it has sufficient body to trigger operation of the equipment. The detector protrudes into the line but it does not extend sufficiently fat into the line that it can possibly snag or otherwise hang a pig traversing the line. When that occurs, difficulties arise in clearing the line of the stuck pig.
The pig passage indicator of the present disclosure further includes an area which is exposed to the fluid in the pipeline. That is an area where nasty accumulations from the flowing material can otherwise accumulate and create problems. In the instance of petroleum based products and especially with flowing oil which has not yet been processed (for example oil flowing from gathering lines in an oil field) at a refinery, there is the tendency that the oil will form a paraffin coating in the pipeline. This coating can accumulate and does accumulate especially in the areas where the flow is less turbulent. This possibility arises in pig passage indicators where there is an area within the equipment where the oil in the line can fill an unflushed region, and there is a tendency for the paraffin to coat in that area, clogging the equipment. In processing plants, the problem is less associated with coating than it is with the collection of a thin film of the sediment from the processed food which might otherwise harbor and grow underirable bacteria. In that particular instance, the pig passage indicator poses the problem in that it typically includes nooks and crannies inside the equipment which are exposed to the flowing product and which regions may accumulate a coating, and the coating itself may harbor and grow an infestation of undesired bacteria. This device avoids such problems.
The pig passage indicator of the present apparatus is intended for use with a pipeline and is particularly able to handle a pipeline operating at a wide range of pressures. For instance, the present apparatus can be used at pressures prevailing in food processing plants in the range of up to about 150 psi. It likewise can operate with oil lines which operate at pressures up to about 500 psi. There is no reason why the present apparatus will not function successfully at pressures up to about 2,000 psi. Higher pressures can be achieved, but that requires incorporation of additional seals to prevent leakage. Suffice it to say, the present apparatus is adaptive in that, for a given seal construction, it is able to withstand any pressure that occurs within the pipeline and hence within the pig passage indicator. The present apparatus incorporates a first and second seal construction so that pressure within the indicator builds up in a sealed area so that fluid in that area is not commingled with fluid in the pipeline. Impurities from the pipeline therefore do not penetrate and enter into the pig passage indicator of this disclosure.
The two seals just mentioned therefore isolate the fluid within the pig passage indicator to assure purity and cleanliness resulting from this isolation, and they prevent commingling with the fluids in the pipeline.
The present apparatus is therefore summarized as an improved pig passage indicator having a protruding and movable probe which extends into the pipeline. It is forced out of the way on movement of a pig through the pipeline. It contacts the pig with a nose which is shaped so that it will not snag or otherwise trip a pig, and especially a full gauge pig. Moreover, it is constructed so that it can mount at any location along the pipeline and thereby enable detection of pigs traveling along the line. The contact with the pig is made by the protruding movable member which is sensitive to passage of the pig. It is forced radially out of the way from the pipeline. It is forced to move away from the pipeline by means of the pig, operating against a coil spring which otherwise provides a bias. The coil spring is captured within a pressure sealed housing. The movable probe of the present disclosure is connected with an enlarged plunger having a seat for the spring, and the plunger is positioned within a surrounding TEFLON seal sleeve. This sleeve isolated pipeline fluid around the plunger is interior of the tool. The plunger is connected to a movable push rod which, when moved by the plunger, provides mechanical linkage to an indicator mechanism. In one form, the indicator mechanism incorporates a pin which is moved, thereby retracting from holding a flag, which flag moves on release to an alarm condition. Another aspect of the present disclosure includes a flag mechanism which in one embodiment has a weight which is held in a particular position by the lock pin. When the pin is removed, the weight if then free to fall by gravity, rotating a flag from a withdrawn position to an upright or alarm position. This provides a mechanical indication of the equipment's operation. That equipment also cooperates with a magnet which is moved on transfer of motion through an appropriate linkage. When the magnet moves, it is brought into near proximity of a reed switch, and the reed switch detects magnetic movement and forms an output mechanical signal which is triggered by such movement and which in turn forms an indication given to an external observer.